Illuminating-canopy.



PATENTED JUNE 30, 1903.

I. L. 0. WADSWORTH.

ILLUMINATING CANOPY.

APPLIOATIOH IILED ARE. 7, 1898.

F0 IODBLE Qmihwaom UNITED STATES Patented June 30, 1903.

PATENT OFFICE.

FRANK L. O. WADSlVORTI-I, OF WILLIAMS BAY, WVISOONSIN, ASSIGNOR, BYMESNE ASSIGNMENTS, TO PRESSED PRISM PLATE GLASS COMPANY, A CORPORATIONOF WEST VIRGINIA.

ILLUMINATING-CANOPY.

SPECIFICATION forming part of Letters Patent N 0. 732,474, dated June30, 1903.

Application filed April 7, 1898. Serial No. 676,823. (No model.)

To aZZ whom it may concern.-

Be it known that I, FRANK L. O. WADS- WORTH, a citizen of the UnitedStates, residing at WVilliams Bay, in the county of Valworth and Stateof WVisconsin, have invented certain new and useful Improvements inIlluminating-Oanopies, of which the following is a specification.

My invention relates to illuminating struc- 1o tures; and it consists ina construction and arrangement fully set forth hereinafter andillustrated in the accompanying drawings, in which- Figure l is a sideview of a section of a transparent illuminating-panel illustrating myimprovement; Fig. 2, the same designed to meet somewhat differentconditions. Fig. 3 is a diagram illustrating the geometric means ofdetermining the proper angle of inclination of the receiving-face of thepanel or structure and the form of the deflecting elements when thelight is falling upon them in a given direction; Fig. 4., the same asFig. 3, the light falling vertically; Fig. 5, the structure as in placeoutside of awindow or other vertical opening.

The improved structure isintended for use especially as a canopy outsideof the window in a wall, well, area, or other place where the mainproportion of entrance rays available for producing an increasedilluminating effect come from one directionas,for instance, the openingtoward the skyin a narrow street, area, or light-shaft.

The structure consists of a series of prisms P P, which may be separateprism-bars arranged side by side or united in one panel; but in eithercase the entrance-face t is a plain fiat surface which in most caseswill form 0 part of the continuous surface of a prismplate, as in Figs.1 and 2. The prism-faces u. w on the opposite or inner side of thestructure are at an acute angle to each other, preferably arranged sothat the face to is parallel to the plane of refraction of the principalincident rays 1 on the face If, and the face to makes equal angles withthis plane and with the plane of refraction of the emergent rays astraced back through the face n.

One of the greatest difficulties in the use of prism-plates in canopiesheretofore has been to secure the transmission and deviation of theentire body of incident light through the prism-plate in the desireddirection without its being diverted or broken up by reason of theinterference of each prism with the one just below. A number ofcomplicated prism forms have been designed and used to avoid thedifficulty, but these forms have not only been very expensive to make,but have been inefficient in that they send a portion of the light inother than the desired direction. I have discovered in connection withmy work in this class of structures that this interference can becompletely avoided for all deviations of the light of less than a rightangle and all the advantages of the simple prism forms retained by firstdesigning the prism forms as above set forth, and, second, by placingthe plane of the entrance 7o face t of the illuminating structureparallel to a plane bisecting the angle between the principal incidentrays (those which come from the main source of illumination and which itis therefor-e most necessary to transmit in the desired directionwithoutanybreak ing up or loss) and the principal emergent rays (inother words, the angle of deviation or deflection of these rays by theprisms) on the other side of the structure. Thus, as shown in Figs. 1and 2, which illustrate two cases in which the direction of theprincipal incident rays 1 1 are different, the extreme rays from theupper side of any prism will just clear the point of the prism above,and the entire body of rays will thus be transmitted in the desireddirection 1 1 without loss or breaking up, such as would occur if any ofthe rays emerging from one prism struck the points of prisms above orbelow. It will be evident from an inspection of Figs.

1 and 2, in which the course of the principal incident rays 1 1 throughthe structure are accurately mapped out, that this result can only besecured by making the angle between 5 the principal incident rays 1 1and the receiving-face equal to or less than the angle between this sameface and the principal emergent rays 1 1 The result can be secured bymaking the angle e less than the angle mo but only at a sacrifice ofavailable canopy area (for Windows or openings of given vertical height,which height of course fixes the Width of the emergent beam) and at asacrifice of some additional light lost by reflection at the incidentface If, the loss by reflection increasing as the angle between the faceand the incident rays decreases.i. c., as the angle of incidenceincreases. The principal features of my invention and those which Idesire to secure by Letters Patent, therefore, consist in the discoveryof the condition of maximum efficiency in the action of the canopy incollecting and transmitting the maximum quantity of light in a givendirection through an opening of a given size Without loss or breakingup.

The prism structure is arranged for use Within a frame A, and when thestructure is applied to a window, as in Fig. 5, the frame is so arrangedthat the face may be placed at the proper angle, as determined above, tothe entrance rays, when it will be found that the full body of lightfalling from the principal direction on the face i is transmittedwithout loss or breaking up into the body of the room in the desired andpredetermined direction.

The canopy can be made adjustable, ifdesired, so as to be moved to oneside or the other of the position of maximum efiiciency; but in thiscase an index or fixed stop or other means should be provided on somepart of the structure as, for example, the

mark t' on the bar 7cwhich will indicate deflnitely the proper angle inwhich it should be placed in order to secure the full transmission ofthe principal incident rays, as determined in the manner set forthabove.

It may happen that the direction of the principal incident rays willchange during the day or at diflerent times during the year, in Whichcase I provide any suitable means for indicating the proper position ofthe canopy, at different times-such, for example, as a fixed graduatedscale 7' on the wall of the building opposite to an index on the movingarm m of the canopy-support.

Without limiting myself to the precise construction shown, I claim Anilluminating-canopy consisting of a prism plate with a series of prismson the lower side having two plane faces lb to meeting at an acuteangle, one face to of each prism parallel to the plane of refraction ofthe principal incident rays, and the other face w making equal angleswith the face u and the plane of refraction of the emergent rays tracedback through the face it, and with a plane receiving-face 7, parallel toa plane bisecting the angle of deflection of the principal incidentrays, substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of

